*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}
.clearfix:after,
.clearfix:before{
    clear: both;
    content:"";
    display: block;
}
body{
    background-color: aquamarine;
}
.content{
    width: 1200px;
    margin: 0 auto;
}
.col{
    height: 100px;
    background-color: aqua;
    float: left;
    width: 30.333333%;
}
/*响应式替换的样式*/
@media (max-width: 600px) {
    .content{
        width: 90%;
    }
    .col{
        width: 100%;
        background-color: #e6e6e6;
    }
    body{
        background-color: lightpink;
    }
}
